Monohaloalkenyl benzoates and trihaloalkyl benzoates

ABSTRACT

Monohaloalkenyl benzoates are halogenated to trihalo-substituted alkyl esters of benzoic acid. The halogenated compounds impart flame retardant properties to a variety of polymeric materials.

This is a divisional application of Ser. No. 540,568, filed Jan. 13,1975, now U.S. Pat. No. 4,158,655, patented June 19, 1979; which is adivisional application of Ser. No. 245,387, filed Apr. 19, 1972, nowU.S. Pat. No. 3,879,445 patented Apr. 22, 1975.

FIELD OF THE INVENTION

This invention relates to halogenated compounds. In another aspect, theinvention relates to flame retarded polymeric compositions.

BACKGROUND OF THE INVENTION

Flame retardancy has become a desired property for plastic articles usedfor commercial and household purposes, such as electrical insulation,carpeting, seat covers, and the like. Polymer compositions can be madedifficultly flammable by the incorporation of various flameproofingagents. However, the ease of obtaining flame retardancy in a givenpolymer tends to vary from polymer to polymer. One type of polymer maybe more effectively flame retarded than another, using the same amountsof additives; or, one type of polymer may require increased amounts ofadditives over the requirements of another type of polymer for eachequivalent level of retardancy; or even one polymer species within apolymer class may require more or less flame retarded additive.

The search for novel compounds which can impart effective flameretardant properties to a variety of polymeric compositions continues.

OBJECTS OF THE INVENTION

It is an object of my invention to provide novel compositions of matter.It is a further object of my invention to provide novel halogenatedorganic compounds. Another object of my invention is to provide novelpolymeric compositions possessing improved flame resistance.

Other objects and aspects as well as the several advantages of myinvention will be apparent to those skilled in the arts to which theinvention appertains from consideration of this specification includingthe appended claims.

BRIEF SUMMARY OF THE INVENTION

I have discovered two groups of novel compounds. Novel unsaturatedmonohalo compounds which I have discovered can be termedmonohaloalkenylbenzoate compounds. The benzoyl moiety thereof can besubstituted, and the halogen of these monohaloalkenylbenzoates ischlorine, bromine, or iodine. These monohaloalkenylbenzoates can behalogenated to novel trihalo compounds, 2,3,4-trihaloalkylbenzoatecompounds, in which the additional halogen can be chlorine, bromine, oriodine, the same or different from the first halogen. The2,3,4-trihaloalkylbenzoate compounds impart effective flame retardancyto polymeric compositions. Polymeric compositions containing the novelhalogenated compounds themselves are novel.

DETAILED DESCRIPTION OF THE INVENTION Monohaloalkenylbenzoates

The novel unsaturated monohaloalkenylbenzoate compounds can bedescriptively termed 4-haloalkenyl benzoates. The compounds also can berepresented by the general formula: ##STR1## in which each R representshydrogen or an alkyl, cycloalkyl, aryl, aralkyl, or alkaryl radical; andthe halogen X is chlorine, bromine, or iodine. The R' groups on thebenzene ring each represent hydrogen or a radical such as alkyl,cycloalkyl, aralkyl, alkoxy, or halogen. When R' is halogen, the halogencan be any one or more of fluorine, chlorine, bromine, or iodine. Theinteger indicator a can range from 0 to 5. There appears to be noparticular upper limitation in the size of a particular R or R' group,as far as operability is concerned. Presently preferred compounds fallinto a sub-generic group such that the total number of carbon atoms percompound does not exceed about 20. Presently further preferred is asub-generic group of monohaloalkenyl benzoate compounds wherein a is 0,and presently most preferred are the unsubstituted benzoates in which Ris hydrogen.

Examples of the 4-haloalkenyl benzoates include: 4-chloro-2-butenylbenzoate, 4-bromo-2-butenyl benzoate, 4-iodo-2-butenyl benzoate,4-chloro-2-butenyl p-toluate, 4-chloro-2-butenyl-3,5-dimethylbenzoate,4-chloro-3-phenyl-2-butenyl benzoate, 4-bromo-2-p-tolyl-2-butenyl2,3,4,5-tetramethylbenzoate, 4-iodo-2-ethyl-3-phenyl-2-butenyl benzoate,4-chloro-3-cyclohexyl-2-butenyl benzoate, 4-bromo-2-butenyl2,4,6-tribromobenzoate, 4-chloro-2-butenyl 4-benzyl-benzoate,4-iodo-2-butenyl 3,5-dimethoxybenzoate, 4-bromo-2,3-dimethyl-2-butenylbenzoate, 4-chloro-2-benzyl-2-butenyl 4-isopropylbenzoate,4-iodo-2-ethyl-2-butenyl p-fluorobenzoate, 4-bromo-3-p-tolyl-2-butenyl2,4-dichloro-benzoate, 4-chloro-2,3-diethyl-2-butenyl benzoate,4-bromo-2-methyl-3-phenyl-2-butenyl 3,5-dibromobenzoate,4-iodo-3-m-tolyl-2-butenyl benzoate, 4-chloro-2-butenyl2,4,6-trimethylbenzoate, and the like, of which 4-chloro-2-butenylbenzoate is a presently preferred species.

The novel haloalkenyl esters represented by the general formula (I) canbe prepared by treating an alkali metal benzoate or substituted benzoatewith a 1,4-dihalo-2-alkene using a suitable catalyst such as a phosphineor quaternary phosphonium salt. The alkali metal of the alkali metalbenzoate can be any of lithium, sodium, potassium, rubidium, or cesium.The benzoate radicals correspond as to substituents or lack thereof tothe corresponding portion of the general formula (I) describing my novelmonohalo unsaturated esters. The 1,4-dihalo-2-alkene reactant can berepresented by the general formula: ##STR2## in which R and X are aspreviously defined. The halogens X need not be, although usually are,the same. Presently preferred are the 1,4-dihalo-2-alkenes in which eachR is hydrogen, such as 1,4-dihalo-2-butene, presently preferred being1,4-dichloro-2-butene, 1,4-diiodo-2-butene, and 1,4-dibromo-2-butene.Various 1,4-dihalo-2-butenes can be readily prepared by halogenation of1,3-butadiene or substituted 1,3-butadienes according to processes wellknown in the arts. Other examples of 1,4-dihalo-2-alkene reactantsinclude: 1,4-dichloro-2-phenyl-2-butene, 1,4-dibromo-2-methyl-2-butene,as well as others corresponding to the appropriate moieties for thedescribed 4-haloalkenyl benzoates without repetitious listing, and thelike.

Phosphine or phosphonium salt catalysts include those which can berepresented by the general formulae R₃ "'P or (R₄ "'P)_(m) Y. Theinteger designator m can range from 1 to 3, and m is equal to thevalence of Y. Y can be any anionic group with appropriate valence usefulin quaternary phosphonium compounds as catalysts. R''' representsvarious hydrocarbon radicals such as alkyl, cycloalkyl, aryl, or anycombination thereof, containing up to about 10 carbon atoms per R'''group, although this is governed by availability of materials ratherthan effectiveness or suitability. Examples of suitable phosphinesinclude trimethyl phosphine, trioctyl phosphine, tricyclopentylphosphine, triphenyl phosphine, tribenzyl phosphine,butylcyclohexylphenyl phosphine, and the like. Examples of quaternaryphosphonium salts include ethyltriphenylphosphonium benzoate,tetraethylphosphonium acetate, tetraoctylphosphonium octanoate,tetra(4-tolyl)phosphonium 4-toluate, ethyltriphenylphosphonium chlorideor fluoride or bromide, or any of the equivalent cyanide, cyanate,isocyanate, sulfate, phosphate, sulfonate, and the like quaternaryphosphonium salts.

From about 0.1 to 50 moles or more of catalyst can be employed per 100moles of alkali metal carboxylate employed in the reaction, although arange of about 0.5 mole to 10 moles presently is preferred.

As can be observed from consideration of reaction, the equivalent ratioof the 1,4-dihalo-2-alkene to the alkali metal benzoate is 1:1, althougha broad range can be employed of up to about 500:1 or even more, with apresently preferred range of about 2:1 to 10:1. It appears desirable toemploy an excess of 1,4-dihalo-2-alkene reactant in order to maximizeyields of the desired haloalkenylbenzoate ester.

In general, any convenient contacting temperatures can be employeddepending on the particular reactants and general reaction parameters.An exemplary temperature would be a range of about 50° C. to 200° C.Pressure preferably should be sufficient to maintain the reactantssubstantially in a liquid phase, such as from about 0.5 atmosphere to 10atmospheres, depending to some extent on temperatures and diluentsemployed. Reaction times sufficient to effect the degree of conversiondesired should be employed, and range from a few minutes to upwards of48 hours or more.

The treating of the alkali metal benzoate with the 1,4-dihalo-2-alkeneusing the above-described catalysts presently preferably employssubstantially anhydrous conditions, although minor traces of water oftenassociated with the reactants do not interfere unduly.

The use of a diluent is a convenience, although the reaction can becarried out in excess 1,4-dihalo-2-alkene such that the1,4-dihalo-2-alkene then acts both as reactant and as reaction medium ordiluent, thus avoiding the use of an extraneous material. Examples ofsuitable diluents include acetone, methyl ethyl ketone, methyl isobutylketone, tetrahydropyran, cyclohexanone; any of the aromatic solventhydrocarbons such as benzene, toluene, xylenes, and the like; aliphatichydrocarbons such as pentane, hexane, and octane; tetrahydrofuran,N,N-dimethylformamide, cyclododecanone, N-methylpyrrolidone, and thelike, alone, or in admixture with each other.

The resulting 4-haloalkenyl esters can be recovered by stripping,solvent extraction, distillation, and the like, as necessary orconvenient.

Trihaloalkyl Benzoates

The novel unsaturated monohalo esters of my invention are used toprepare novel 2,3,4-trihaloalkyl esters of benzoic acid which are afurther part of my invention. The 2,3,4-trihaloalkyl esters of benzoicacid can be represented by the general formula: ##STR3## wherein R, R',a and X, are as defined hereinbefore, with the halogens in the two- andthree-position being the same.

The novel 2,3,4-trihaloalkyl benzoates conveniently are prepared by theaddition of halogen to the corresponding 4-haloalkenyl esters. Suchhalogenation can be carried out at moderate temperatures, i.e., fromabout -20° to +50° C., using a solvent such as chloroform, carbontetrachloride, carbon disulfide, or the like, under halogenationconditions convenient for halogenation of unsaturated materials. Areaction interval of several minutes to several hours, such as from 1hour to 12 hours, should be sufficient. If desired, a minor trace ofhydrogen halide can be added as a catalyst, or a mixture of halogen andaluminum halide in an alcohol such as ethanol can be used. Generally anexcess of halogen is avoided, so that a 1:1 molar ratio of halogen tounsaturated benzoate presently would be preferred. Examples of the noveltrihalobenzoates include any of the hereinbefore described 4-haloalkenylbenzoates which have been halogenated so as to add halogen to the doublebond to become trihaloalkyl benzoates, such as 4-chloro-2-butenylbenzoate to 2,3-dibromo-4-chlorobutyl benzoate, without needlesslyrepeating a list of exemplary species.

Flameproofed Polymer Compositions

The novel trihalo compounds of my invention are useful as flameretardant additives for polymeric compositions. These additives can beemployed, for example, in compositions of thermoplastic polymers.

Suitable polymers include any of the thermoplastic polymericcompositions such as the polydienes, i.e., the homopolymers andcopolymers of conjugated dienes having from 4 to 10 carbon atoms permolecule, such as butadiene, piperylene, isoprene, chloroprene,1,5-hexadiene, and the like, including copolymers withmonovinyl-substituted aromatic compounds of up to 12 carbon atoms permolecule. Presently of importance because of wide textile usage arepolymers of the aliphatic 1-monoolefins known generally aspolymonoolefins. These polymers include homopolymers and copolymers ofaliphatic 1-monoolefins having at least 2 carbon atoms per molecule,usually 2 to 8 carbon atoms for commercial availability, such aspolyethylene, polypropylene, copolymers of ethylene and propylene, orcopolymers of such monomers with minor amounts of monomerscopolymerizable therewith such as ethylene, propylene, 1-butene,1-hexene, 1-octene, monovinyl-substituted aromatic compounds of up to 12carbon atoms such as styrene, alpha-vinyl naphthalene, p-isopropylstyrene, p-methyl styrene, and the like. Other polymeric substancesemploying flame retardants include a wide variety of other polymers suchas the poly(vinyl halides) such as poly(vinyl chloride); cellulose;acrylic resins; and the like.

The trihaloalkyl esters of my invention should be employed in polymercompositions in such minor amounts as are effective in providing thedesired degree of flame retardancy to the particular polymer or in thepolymeric composition involved, which amount can vary over a broadrange, depending on the polymer characteristics and the degree ofprotection desired or required. The presently preferred range ofadditive is about 3 to 30 parts per 100 parts of polymer, presently morepreferred in an amount within the range of 5 to 10 parts, excludingother additives, fillers, colorants, and the like.

Antimony oxide, presently preferred as the trioxide, can be employedwith halogenated additives to enhance the effectiveness of organic flameretardants, such as from about 0.5 to 20 parts of antimony trioxide per100 parts of polymer. A typical weight ratio of halogenated additive toantimony oxide would be about 0.1:1 to 10:1, presently preferred about2:1. Other useful oxides include bismuth oxide and arsenic trioxidewhich can be used, if desired, in place of or even with the antimonytrioxide for this purpose.

EXAMPLES

The examples and runs described herein are intended to illustrate myinvention. Particular components described and conditions employedshould be considered illustrative and not limitative of the reasonablescope and extent of our invention.

EXAMPLE I

To a dry stirred autoclave were added sodium benzoate 20 g, 0.14 mole,ethyltriphenylphosphonium bromide 1.2 g, 0.003 mole, and1,4-dichloro-2-butene 37.5 g, 0.30 mole, in 50 ml of 2-butanone. Thesystem was flushed with dry nitrogen. The stirred mixture was heated to110° C., held at this temperature for 2.5 hours, then cooled to roomtemperature. The solid material was filtered off, washed with 25 ml of2-butanone, and air dried to give 8.8 g residue (8.2 g of NaCltheoretical).

The solvent in the filtrate was removed in vacuo to leave 43 g of ayellow liquid. Ether was added and the resulting tan solid removed byfiltration and shown to be ethyltriphenylphosphonium bromide by infraredanalysis.

The etheral filtrate was washed with 100 ml of distilled water and theorganic layer was separated and dried over anhydrous magnesium sulfate.The ether was removed in vacuo to give a yellow liquid. Unreacted1,4-dichloro-2-butene was removed by distillation b.p.ca. 60° C./20 mm.Fractionation of the remaining liquid gave 16 g of ester isolated as aclear colorless oil b.p. 100° C./0.1 mm. This liquid was shown by NMRanalysis to be 4-chloro-2-butenyl benzoate.

EXAMPLE II

To a stirred reactor was added a solution of the 4-chloro-2-butenylbenzoate 10 g, 0.0475 mole in 60 ml of chloroform. A small amount ofsodium bicarbonate was added and the stirred mixture cooled in anice-salt bath. To this was added slowly over about nine hours a solutionof bromine 7.6 g, 0.0475 mole, aluminum chloride 0.15 g, 0.001 mole, andabsolute ethanol 1 ml, in 25 ml of chloroform. Since the brominereaction was slow the solution was allowed to warm to room temperature.The resulting straw colored solution was stirred overnight at roomtemperature. The solution was washed with distilled water, 5 percentaqueous sodium bicarbonate, and again with distilled water. The organiclayer was separated, dried over anhydrous magnesium sulfate, andconcentrated in vacuo to leave 16.9 g of a colorless oil. Infrared andNMR spectra of this oil indicated it to be 2,3-dibromo-4-chlorobutylbenzoate.

EXAMPLE III

The following data demonstrate the flame retarding properties of the2,3-dibromo-4-chlorobutyl benzoate in a polymer composition.Polypropylene was compounded with varying amounts of the trihalobenzoateand with antimony trioxide, the latter frequently employed to assistflame retarding effects of halogenated compounds, although by itself itexhibits no such properties.

                  TABLE I                                                         ______________________________________                                                            Limiting                                                                      Oxygen Index                                              Benzoate, phr                                                                           Sb.sub.2 O.sub.3, phr                                                                   ASTM D-2863 ASTM D635                                     ______________________________________                                        2         1         21.5        burned                                        3         1.5       23.4        burned                                        5         2.5       24.5        self-extinguishing                                                            to nonburning                                 ______________________________________                                    

These data demonstrate that the trihalobenzoates can be used foreffective flame retarding in polymeric composition.

The polymeric compositions of my invention using the novel flameretardant can be compounded with other additives such as thermalstabilizers, fillers, pigments, dyes, plasticizers, and the like, any orall of which can be added to the formulation to improve stability and/orother properties of the final polymer composition for various purposes.

Reasonable variations and modifications of my invention are possiblewhile still within the scope of my disclosure, and without departingfrom the intended scope and spirit thereof, as detailed in myspecification and the claims appended.

I claim:
 1. Unsaturated monohaloalkenyl benzoate compounds representedby the general formula ##STR4## in which each R is individually selectedfrom hydrogen and a radical which is alkyl, aryl, aralkyl, or alkaryl; Xis halogen and is chlorine, bromine, or iodine; each R' is individuallyselected from hydrogen or a radical which is cycloalkyl, aralkyl, oralkoxy, such that at least one R' is cycloalkyl, aralkyl, or alkoxy; ais an integer and is 5; and wherein the total number of carbon atoms persaid unsaturated monohaloalkenyl benzoate compound does not exceed 20.2. Unsaturated monohaloalkenyl benzoate compounds according to claim 1selected from the group consisting of 4-iodo-2-butenyl3,5-dimethyloxybenxoate, or 4-chloro-2-butenyl 4-benzylbenzoate.
 3. Thecomposition according to claim 1 wherein R' is cycloalkyl.
 4. Thecomposition according to claim 1 wherein said R' is aralkyl.
 5. Thecomposition according to claim 1 wherein R' is alkoxy.
 6. Themonohaloalkenyl benzoate compounds according to claim 1 wherein each Ris hydrogen.
 7. The monohaloalkenyl benzoate compounds according toclaim 6 wherein X is chlorine.